The present invention relates to a video surveillance system having a camera malfunction detection function of detecting a video acquisition failure due to an obstruction to a camera or equipment fault in a video surveillance system (surveillance camera system) which acquires videos from an imaging device such as a camera and has a function of intruder detection by image recognition.
The video surveillance system has a function of detecting a moving object such as a person and vehicle which appear in a surveillance area based on image recognition from a video acquired from a camera. By using detection results, the video surveillance system draw a warder to attention by using a function of storing only videos in which moving objects appear, a display of a warning icon on a display device, or ringing of a buzzer. Therefore, the video surveillance system serves to reduce a load of a watching service in which a continuous confirmation work is necessary. In addition, in the above-described video surveillance system, when dishonesty such as theft is caused, the stored video can serve to attest to the crime afterward.
With respect to the above-described video surveillance system, problems by conducts occur such that a criminal changes an imaging angle of the camera, places shielding in front of the camera, or causes harm to a camera lens so that evidential videos may not be acquired. Since video signals themselves can be acquired in the case of these conducts, useful videos cannot be acquired unless visual checking is performed.
Further, when a failure of the imaging device itself is caused, videos can not be acquired naturally so that the video surveillance system may be deactivated. A malfunction of the device needs to be acknowledged to the warder, the malfunction of the camera need to be repaired, and the video surveillance system needs to be restored.
To cope with the above-described problem, a method for detecting a change in an image by image recognition, and detecting a malfunction of a camera is disclosed, for example, in JP-A-2001-6056, JP-A-2008-77517, and JP-A-2009-193464. In JP-A-2001-6056, disclosed is a technology in which an infrared LED is provided as an auxiliary illumination, a photo sensor detecting the brightness of monitoring environment is provided, and a unit which detects obstruction to a camera through the above-described detectors is provided. In JP-A-2008-077517, the following technology is disclosed: An input image is compared with a reference image to calculate a change in each pixel. From this result, by using a subtraction or dispersion of luminance, it is checked whether it is a single color blocking action to cover a camera and make the image only one black or white, or a mixed change blocking action to change a direction of the camera and change the entire image. In JP-A-2009-193464, disclosed is a technology in which image data is divided into multiple blocks, a standard deviation value and a variation of luminance value are calculated in each block to detect whether the camera is covered.